Getter-containing electric discharge devices

ABSTRACT

An open-ended non-vaporizable getter element is secured to an anode axial bore of a disk-seal electric discharge tube with a sleeve-like tubing seal. The getter element comprises an openended container, as of molybdenum, filled with a sintered highly porous mixture of at least 70 percent by weight of zirconium and up to 30 percent by weight of carbon. The getter element is soldered to the bore walls and to the tubing seal during initial assembly of the discharge tube.

United States Patent Maegdefessel et al. Apr. 2, 1974 [5 GETTER-CONTAINING ELECTRIC 1,937,706 12/1933 McCullough 313/174 DISCHARGE DEVICES 3,719,433 3/1973 Rabusin 313/181 X [75] Inventors: Heinz Maegdefessel, Haslach; I-Iari FOREIGN PATENTS 0R APPLICATIONS Verma, Krailling, both Of 2 005 2 2 2 9 9 France Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin & P i y ExaminerJames W. Lawrence MuniCh, Germany Assistant Examiner-Wm. H. Punter [22] Filed, Nov 2 1972 Attorney, Agent, or Firm-Hill, Sherman, Meroni,

Gross & Simpson [21] Appl. No.: 303,106

57 ABSTRACT [30] Foreign Application Priority Data 1 Nov 10 971 Germany 2155875 An open-ended non-vaporizable getter element is secured to an anode axial bore of a disk-seal electric dis- 52 US. Cl. 313/174 313/7 charge tube with a sleeve'like tubing Seal- The [51] Int. Cl. H016 19/70 element comprises an open'ended container as of Field f Search u 181 7 7 lybdenum, filled with a sintered POI'OUS mixture 1 of at least 70 percent by weight of zirconium and up to 30 percent by weight of carbon. The getter element [56] References Cited is soldered to the bore walls and to the tubing seal during initial assembly of the discharge tube.

5 Claims, 1 Drawing Figure GETTER-CONTAINING ELECTRIC DISCHARGE DEVICES CROSS-REFERENCE TO RELATED APPLICATION stant assignee.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to electric discharge devices and more particularly to getter-containing electric discharge tubes. I

2. Prior Art It is known to completely enclose vaporizable getter materials within a container and positioned thesame within an electric discharge tube so that a getter material mirror-like film is produced on the envelope of the tube, as by HE (high frequency) annealing. A serious drawback with such vaporizable getter. material is that it is difiicult to controlthe getter material vapors and it is extremely important to avoid depositing getter material film on any-important parts of a discharge tube, particularly on any insulating parts thereof.

Such drawbacks are substantially eliminated with non-vaporizable getter materials, however, nonv'aporizable getter materials must be heated, either periodically at a desired repetition rate or continuously by special heating devices within the discharge tube, thereby rendering such getters uneconomical. I

The invention provides a getteredelectric discharge device that substantially eliminates the prior art drawbacks.

SUMMARY OF THE INVENTION The invention provides a gettered electric discharge device wherein the gettered element includes a nonvaporizable' gettering material that is adequately degassed at temperatures in therange of 450 to 600 C.,

I even when heating in a protective gas atmosphere has BRIEF DESCRIPTION OF THE DRAWINGS The single FIGURE is an. elevated schematic side view, partially in section, illustrating an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention provides electric discharge devices, particularly disk-seal electric discharge tubes having an evacuation bore therein, having a non-vaporizable getor carbon. In practice, a gettering mixture consisting of about 83 percent by weight of zirconium and about 17 percent by weight of graphite (carbon) has particular advantages.

A getter element is preferably formed into an annular body so that the gettering materialis exposed along the inner surface thereof, however, other forms of getter elements are also useful. The getter element is positioned in an axial bore communicating with an anode of an electric discharge device and soldered thereto, along with a sleeve-like tubing seal so as to prevent it from accidentally breaking loose from the bore walls.

The preferred gettering material has such cohesion to the various particles thereof as well as to the container thereof that no protective measures have to be undertaken to prevent portions of the gettering mass, i.e., particles thereof, from fallingout of the getter element.

Zirconium-carbon mixtures have been previously utilized in systems that could be heated either'periodically at any desired repetition rate orcontinuously, such as a layer on a heating coil or filament insulated with aluter element secured within such bore and designed for tered highly porous mixture of at least 70 percent by weight of zirconium and up to about 30 percent by weight of carbon. The container is composed of a hightemperature resistant material, such as of molybdenum minum oxide. During a systematic investigation of such systems, it was discovered that zirconium-carbon mixtures may be utilized in different forms to obtain increased gettering capacity. Theproperties of such mixtures, particularly in a sintered highly porous condition, allows formation of getter members which are only heated once during the production process of a particular discharge device. This single heating step drives suf- Y ficient gas from the gettering material so that it attains a large gettering capacity over a long period of time,

even in a cold state. Another outstanding feature of the zirconium-carbon gettering material is the excellent adhesion such material exhibits toward an appropriate base. Further, this gettering mixture has excellent internal cohesion to its own particles so that no loose particles occur and the gettering mixture may be formed into very thick layers. Such thick gettering mixture layers have a gas absorption capacity which even in the cold state exceeds the gas absorption capacity of heretofore known gettering materials.

Referring now to the drawings, the single FIGURE illustrates an electric discharge disk-seal tube '1. The various conventional electrodes of such a tube are not shown and only a partial sectional view of the anode la is shown. The anode 1a has a central or axial bore 2 for evacuation of the tube 1. The upper portion, such as at 3 of axial bore 2, is of a wider cross-section than the lower portion thereof. Normally, a sleeve-like tubing seal 4 is positioned along the upper portion 3 of bore 2 so as to abut on the flange-like surfaces 3a joining the narrower cross-section portion of the bore with the wider cross-section portion 3 and is directly soldered thereto.

In accordance with the principles of the invention, a

getter element 7 is positioned between the flange-like surface 3a and the lower surfaces of the tubing seal 4. The getter element 7 consists of an annular container 5, such as composed of sheet molybdenum, which is open to the interior of bore 2. A sintered highly porous zirconium-carbon gettering mixture 6 is positioned within the container 5. Once the getter element 7 and the tubing seal 4 are properly positioned within the bore 2, they are both soldered to the bore walls along with other parts of the discharge device assembly,

under a protective gas atmosphere. Once properly secured, no further heating of the getter element is required for operation.

In assemblies where the axial bore is a part of the actual discharge chamber, the insertion of a getter element in accordance with the principles of the invention does not interfere with the normal operation of such a discharge assembly.

The getter element is secured to an electric discharge device by hard soldering at about 850 C. in a protective gas atmosphere consisting of a conventional composition, i.e., H and N in a ratio of about 20 percent:80 percent. During evacuation of the electric discharge tube, subsequent heating of only up to about 400 to 600 C. occurs. Despite such low temperature heating of the getter element, it is surprisingly highly effective, even at room temperatures.

The invention provides, among other things, a means of incorporating a getter element into any electric discharge device having an evacuation bore in a simple and highly economical manner. The invention does not require any modification of the production method utilized in assembling a given electric discharge device. Further, the invention does not alter in any disadvantageous manner the normal function of a given electric discharge device.

As is apparent from the foregoing specification, the present invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto-appendant claims.

We claim as our invention: 1. In an electric discharge device including an anode having an evacuation bore and a tubing seal means mating with a portion of said bore, the improvement comprising, a non-vaporizable'g'etter element consisting of an open-ended container formed of a hightemperature resistant material and a gettering mass within such container consisting of a sintered highly porous mixture of at least percent by weight of zirconium and up to 30 percent by weight of carbon, said getter element being positioned within said evacuation bore adjacent said tubing seal means and attached to the bore walls and tubing seal means by solder.

2. In an electric discharge device as defined in claim 1 wherein said getter element and said tubing seal means are soldered together during an initial assembly of said discharge device.

3. In an electric discharge device as defined in claim 1 wherein said open-ended container is composed of molybdenum.

4. In an electric discharge device as defined in claim 1 wherein said device is a disk-seal tube.

5. An electric discharge device comprising a housing including a cathode and an anode positioned therein in working relation to each other, said anode including an evacuation bore having one portion of a given crosssection, another portion of a larger cross-section and flange-like surfaces joining said portions to one another; a getter element comprised of an annular openended container composed of a high-temperature resistant material and a gettering mass within such container consisting of a sintered highly porous mixture of at least 70 percent by weight of zirconium and up to 30 percent by weight of carbon, said getter element being positioned within said evacuation bore on the flangelike surfaces thereof; and a sleeve-like tubing seal means positioned within said evacuation bore at the larger cross-section portion thereof and on said getter element, said tubing seal means and said getter element being secured to said evacuation bore by solder. 

2. In an electric discharge device as defined in claim 1 wherein said getter element and said tubing seal means are soldered together during an initial assembly of said discharge device.
 3. In an electric discharge device as defined in claim 1 wherein said open-ended container is composed of molybdenum.
 4. In an electric discharge device as defined in claim 1 wherein said device is a disk-seal tube.
 5. An electric discharge device comprising a housing including a cathode and an anode positioned therein in working relation to each other, said anode including an evacuation bore having one portion of a given cross-section, another portion of a larger cross-section and flange-like surfaces joining said portions to one another; a getter element comprised of an annular open-ended container composed of a high-temperature resistant material and a gettering mass within such container consisting of a sintered highly porous mixture of at least 70 percent by weight of zirconium and up to 30 percent by weight of carbon, said getter element being positioned within said evacuation bore on the flange-like surfaces thereof; and a sleeve-like tubing seal means positioned within said evacuation bore at the larger cross-section portion thereof and on said getter element, said tubing seal means and said getter element being secured to said evacuation bore by solder. 